Prior to its formation, the names of satellites have had varying histories. The choice of names is often determined by a satellite's discoverer; however, historically some satellites were not given names for many decades or even centuries after their discovery.

Mars

Jupiter

The Galilean moons of Jupiter (Io, Europa, Ganymede and Callisto) were named by Simon Marius soon after their discovery in 1610. However, by the late 19th century these names had fallen out of favor, and for a long time (until the mid 20th century) it was most common to refer to them in the astronomical literature simply as "Jupiter I", "Jupiter II", etc., or as "the first satellite of Jupiter", "Jupiter's second satellite", etc.

The moons of Jupiter discovered between 1904 and 1951 were not named until 1975, being known until then simply by their Roman numeral designations (Jupiter VI through Jupiter XII). The moon Amalthea (Jupiter V), discovered in 1892, was unofficially named but its name was also not made official until 1975. Since the names of the Galilean satellites themselves had fallen out of favor, it is perhaps not unusual that the discoverers of the new smaller satellites did not see fit to name them either.

Current practice is that newly discovered moons of Jupiter must be named after lovers of the mythological Jupiter (Zeus). A convention has also emerged among the outer moons, whereby prograde moons are given names ending in 'a' or 'o', and retrograde moons receive names ending in 'e'. In 2004, with new Jovian moons continuing to be discovered, these rules were found to be excessively restrictive, and so the IAU agreed to permit moons to be named after Zeus's descendants as well.

Saturn

The seven known moons (at the time) of Saturn were named in 1847 by John Herschel. Herschel's system was to name Saturn's moons after the mythological Greek Titans. Until then, Titan was known as the "Huygenian (or Huyghenian) satellite of Saturn" and the other moons had Roman numeral designations in order of their distance from Saturn. Subsequent discoverers of Saturnian moons followed Herschel's scheme: Hyperion was discovered soon after in 1848; the ninth moon, Phoebe was named by its discoverer in 1899 soon after its discovery; and the name of Janus was suggested by its discoverer, Audouin Dollfus.

Current IAU practice for newly discovered inner moons is to continue with Herschel's system, naming them after Titans or their descendants. However, the increasing number of moons that were being discovered in the 21st century caused the IAU to draw up a new scheme for the outer moons, which are named after giants in the mythologies of other cultures. Since the outer moons fall naturally into three groups, one group is named after Norse giants, one after Gallic giants, and one after Inuit giants. The only moon that fails to fit this scheme is the Greek-named Phoebe, which is in the Norse group.

Subsequent naming choices have accorded with Herschel's choices. In 1949, the fifth moon, Miranda, was named by its discoverer after a character in Shakespeare's The Tempest. Current IAU practice is to name moons after characters from Shakespeare's plays and The Rape of the Lock (although the names from Shakespeare far outnumber those from Pope). At present, the outermost moons are all named after characters from one play, The Tempest.

Neptune

The one known moon (at the time) of Neptune was not named for many decades. Although the name Triton was suggested in 1880, it did not come into general use until the mid 20th-century. In the astronomical literature it was simply referred to as "the satellite of Neptune". Later, the second known moon, Nereid, was named by its discoverer in 1949 soon after its discovery.

Current IAU practice for newly discovered Neptunian moons is to accord with these first two choices by naming them after Greek sea deities.

See also

References

John Herschel names the seven known satellites of Saturn: MNRAS 8 (1848) 42 (http://adsabs.harvard.edu//full/seri/MNRAS/0008//0000042.000.html) in his 1847 publication of Results of Astronomical Observations made at the Cape of Good Hope)